Prior art 3D displays have been described in a large variety of publications, including “New Autostereoscopic Display System”, Ezra, Woodgate, Omar, Holliman, Harrold and Shapiro (1995), SPE Proceedings “Stereoscopic Displays and Virtual Reality Systems II” Vol. 2409, pp 31–40; “Retroreflective Screens and their Application to Autostereoscopic Displays” Harman, SPIE Proceedings “Stereoscopic Displays and Virtual Reality Systems IV”, Vol. 3012, pp 145–153; “Stereoscopic Display Employing Head-position Tracking using Large Format Lenses”, Hattori, (1993), SPIE Proceedings “Stereoscopic Displays and Applications IV” Vol. 1915, pp 2–5; “Three-Dimensional Display with Focused Light Array” Kajiki, Yoshikawa, and Honda (1996), SPIE Proceedings “Practical Holography X” Vol. 2652 pp 106–116; “Perfect 3-Dimensional Movies and Stereoscopic Movies on TV—and Projection Screens; An Appraisement”, Klein and Dultz (1990), SPIE Proceedings “Stereoscopic Displays and Applications” Vol. 1256, pp 289–295; “Stereoscopic Liquid Crystal Display II (Practical Application)”, Nishida, Hattori, Sakuma, Katayama, Omori and Fukyo (1994), SPIE Proceedings “Stereoscopic Displays and Virtual Reality Systems”, Vol. 2177, pp 150–155; “Lenticular Stereoscopic Display System with Eye-Position Tracking and without Special-Equipment Needs”, Omura, Tetsutani and Kishino (1994), SID 94 Digest, pp 187–190; “Head-Tracking Stereo Display: Experiments and Applications”, Paley (1992), SPIE Proceedings “Stereoscopic Displays And Applications III”, Vol. 1669, p88; “Head Tracking Stereoscopic Display”, Schwartz (1985), Proceedings of IEEE International Display Research Conference, pp 141–144; “Parallax Barrier Display Systems” Sexton (1992), IEE Colloquium “Stereoscopic Television” Digest No: 1992/173, pp 5/1–5/5; U.S. Pat. No. 5,712,732; “3D-TV Projection Display System with Head Tracking”, Tetsutani, Ichinose and Ishibashi (1989), Japan Display '89, pp 56–59; “A Study on a Stereoscopic Display System Employing Eye-position Tracking for Multi-viewers”, Tetsutani, Omura and Kishino (1994), SPIE Proceedings “Stereoscopic Displays and Virtual Reality Systems”, Vol. 2177, pp 135–142; “Autostereoscopic Display using Holographic Optical Elements”, Trayner and Orr (1996), SPIE Proceedings “Stereoscopic Displays and Applications VII”, Vol. 2653, pp 65–74; “Developments in Autostereoscopic Displays using Holographic Optical Elements”, Trayner and Orr (1997), SPIE Proceedings; and “Observer Tracking Autostereoscopic 3D Display Systems”, Woodgate, Ezra, Harrold, Holliman, Jones and Moseley (1997), SPIE Proceedings “Stereoscopic Displays and Virtual Reality Systems IV”, Vol. 3012, pp 187–198.
3D displays have been used in a variety of niche applications for many years, and as the quality of the display systems has improved, so too has the range of applications. Broadcast television is probably the largest potential application, however the requirements of a television system are complex and few, if any, existing display systems can meet these requirements.
There are various desirable requirements for a display suitable for a broadcast television system. It would be desirable to provide a display that can present stereo images to several viewers who will occupy a typical ‘living room’ sized region. Such a system is more complex than those intended for single viewers proposed, for example, for computer monitor or arcade game applications.
The overall size of the display should preferably not be excessive, as is the case with some systems, for instance those where there is a moving pair of projectors for each viewer. A basic requirement for a domestic television display is that it will fit through a door. The size of the proposed display will be in the order of that of current back-projected televisions.
Some prior art autostereoscopic displays operate by providing regions in front of the screen where a left image only is seen across the complete width of the screen, and adjacent regions where a right image only is seen. These regions are referred to as the exit pupils. The positions of these exit pupils follow the viewers' eye positions by being controlled by the output of a head position tracker that determines where the viewers' eyes are located in front of the screen. The advantage of head tracking is it ensures nothing is displayed that is not actually seen by a viewer, thus placing the least demands on the amount of information that has to be displayed.
Referring to FIG. 1, in principle, an exit pupil could be formed with a large lens 9 located close to the LCD display, with an illumination source 8 positioned behind it. Consider an eye located at the exit pupil 10 in FIG. 1(a); in this position it will observe illumination over the complete area of the lens. When away from the pupil, the eye will see either no illumination or illumination over part of the lens only.
However, this would be an impracticably large configuration for a display. In FIG. 1(b) it can be seen that the single large lens can be replaced by an array of lenses 12 each with its own small light source 11. The sources 11 all lie in one plane. In this case, the exit pupil 13 is formed from a bundle of approximately parallel rays from array 12 as opposed to the continuously converging rays from lens 9.
Prior art systems which use an array of cylindrical lenses for producing vertical exit pupils have drawbacks when used in a 3D display. Firstly, off-axis aberrations limit the off-axis performance so that the display would not provide exit pupils over a region sufficiently wide for multiple-user applications. Secondly, it is difficult to make the boundaries between the lenses invisible.